This invention relates to in-line sewer pipe cleaners and, more particularly, to an improved, self-propelled, hydraulic in-line tap cutter.
Sewer mains or sewer pipes are placed along streets and highways below the surfaces thereof in virtually every city in the United States having a substantial population. Generally, access to sewer mains is gained by means of vertical conduits referred to as "manholes." Sewer pipes are commonly 6" or 8" in diameter with manholes spaced apart more or less at regular intervals of, say 400 feet.
Many modern building codes require that, when a sewer line from a residence or other building is tapped into the sewer main, the connection must be made according to certain prescribed standards with little or none of the tap line extending into the sewer main. Prior to the adoption of such codes however, tap connections sometimes were made which protrude substantially into the sewer pipe. Such tap connections (or simply "taps") were satisfactory for most purposes, but the protruding portions of such taps constitute a trap for leaves, roots, and other debris. When debris accumulates in a sewer pipe, it clogs or at least restricts flow in the sewer main. Metal fence posts and anchor stakes for pole support cables are sometimes driven through sewer pipes. These, too, form obstacles that lead to clogging, as do roots of trees which commonly intrude in sewer lines.
When sewer pipes become completely or substantially blocked, it of course interferes with the operation of the sewage system and the blockage must be cleared. One method of clearing such blockages is to dig a hole in the ground over the sewer pipe at the location of the obstruction, down to the level of the sewer pipe, break into the pipe, remove the debris, and replace the affected section with new pipe.
Cleaning a sewer pipe as described is extremely expensive due to the manpower and equipment required for such tasks and, therefore, is preferably avoided. Toward that end, devices have been proposed for cleaning sewer pipes by operating inside the sewer pipe to be cleared, hence the name "in-line" pipeline cleaner.
In-line pipeline cleaners that are known are generally acceptable for clearing leaves, tree roots, and other kinds of soft debris from a sewer pipe. Examples of such devices are shown in U.S. Pat. Nos. 3,740,785 to Latall; 4,516,286 to Crane; 3,844,362 to Albert; 3,562,836 to Frew and 1,426,919 to Sladen. Devices such as those shown in the aforementioned patents generally include some type of rotating bit or brush on the front end. In use, such cleaning devices are inserted into a sewer pipe at a manhole and are transported through the pipe to clean it and clear obstructions. The devices shown in those patents are not acceptable for cutting taps or other hard obstructions for several reasons explained below.
One of the important considerations in cutting taps is the need to propel the tap cutter through the pipe with a force sufficient to drive the rotating bit through the intruding tap to cut it. Adequate force may be provided manually by pulling the tap cutter through the pipeline using a cable. Examples of tap cutters designed to be dragged through the pipe by a cable are shown in U.S. Pat. Nos. 3,587,194 to Brown and 4,657,449 to Marich et al. Those machines are expensive to use because their operation requires a two-person crew; a first person positioned at one manhole upstream of the tap cutter to pull it through the pipe, and a second person positioned at a downstream manhole to operate the hydraulic or other fluid lines provided to operate the tap cutter and control the necessary pump.
Labor expense can be reduced substantially by employing a self-propelled tap-cutting apparatus that can be operated by one person. An example of a self-propelled apparatus for clearing soft materials is shown in U.S. Pat. No. 4,516,286, mentioned above. That apparatus, however, is designed for cleaning away roots and other soft debris but is not adequate to cut taps. A suitable cutting bit is not disclosed in the in-line sewer pipe cleaning art. Additionally, even with an appropriate tap cutting bit, the apparatus shown in U.S. Pat. No. 4,516,286 would be ineffective for cutting taps over a sufficiently long distance to reach between manholes, for example, 400 feet. Drag due to the skids provided on that apparatus (reference numeral 14) would leave inadequate forward force to cut a tap.
An important object in tap cutting is to cut off the tap as close as possible to the sewer pipe interior wall, to minimize the accumulation of debris behind (i.e. upstream of) the tap. U.S. Pat. No. 4,657,449 shows an apparatus directed to cutting a tap close to the sewer pipe wall. That apparatus employs a relatively small cutting bit, radially positionable about the longitudinal axis of the apparatus. Such an arrangement would not work for cutting large taps. For example, it is not uncommon to encounter taps which are only slightly smaller than the sewer pipe into which they feed, for example, a 6" tap in an 8" line. In that circumstance, an apparatus of the type shown in '449 simply would jam up and stop, or perhaps damage itself.
An approach useful for cutting larger taps is to employ a cutting head or bit having a diameter only slightly less than the diameter of the sewer pipe in which the tap cutting apparatus is to be used. A tap cutting apparatus of that sort is shown in U.S. Pat. No. 3,587,194 to Brown. That apparatus, however, and others like it, are inclined to hang up or become stuck at offsets in the sewer pipeline due to its length. It also requires two people to use it, and its design is very complex.
Another problem encountered in clearing taps from sewer pipes is breakage of the sewer pipe. Excessive jarring, shaking and knocking against the pipe is likely to break the pipe, particularly an older pipe made of concrete aggregate. Another problem which results from attempts to cut a tap involving undue shaking and jarring is breaking or cracking the tap at a position outside of the sewer main. Either of these circumstances requires digging up the pipeline to repair the pipe, thereby nullifying the advantages of using an in-line tap cutting device. For example, the apparatus shown in U.S. Pat. No. 3,562,836 to Frew et al. appears likely to cause such damage in the event it encounters a protruding pipe connection, because of its blunt reaming head.
Accordingly, it is an object of the present invention to provide a method and an in-line tap cutting apparatus that are effective for clearing taps and other hard obstructions from sewer lines.
A second object of the present invention is to provide a self-propelled tap cutter capable of operating effectively at a substantial distance from a pressurized water source.
Another object of the present invention is to enable a single worker to clear taps from a sewer pipe, operating an in-line tap cutter over substantial distance, with minimal risk of jamming.
A further object of the present invention is to cut away a tap of a diameter up to approaching that of the sewer pipe without breaking the sewer pipe or cracking the tap outside the sewer pipe.
Another object of the present invention is to enable an in-line tap cutter to travel through a sewer pipe and cut taps close to the interior wall of a sewer pipe without jamming at offsets in the pipe.